This invention relates to equipment for preparing asphaltic rubber mixes for use in paving.
It is known that asphalt rubber mixes are beneficial as elastomeric paving materials. Mixtures of rubber and asphalt have been used extensively for over one hundred years in an effort to combine the resiliency and wear resistance of the rubber with the strength of asphalt. Examples are shown in U.S. Pat. Nos. 2,310,972; 2,700,655; 2,578,001; 3,049,836; 3,253,521; 3,270,631; 3,338,849; 3,340,780 and 3,844,668.
Various mixtures have been tested but a typical prior art mixture is shown in McDonald U.S. Pat. No. 3,891,585 and Winters, et al, U.S. Pat. No. 3,844,668. These mixtures, and all prior art high rubber content rubber asphalt compounds have been characterized by high viscosities, a gel like state, lengthy processing times to form the mixture and relatively short pot life for the resulting mixture
These patents reveal various processes for mixing asphalt and rubber, but the basic steps known are to mix asphalt from 350 to above 500 degrees fahrenheit, mixing in ground rubber in a high shear mixer which physically abrades the rubber particles to produce reacted product, and then holding the mixture at that temperature until the rubber is substantially reacted with the asphalt. Reported times for this prior art reaction are about one-half to one hour after rubber induction to form the material which at its end point is reported to have an extreme viscosity, between 2,000 to about 50,000 centipoise, but ranging as high as 150,000 to 200,000 centipoise. Special equipment is reported to be required to handle the resulting mixtures.